I spoke with Valdis Krebs this afternoon who was high over the Atlantic flying SAS on his way home from eastern Europe. He was talking to me using Skype, and not paying anything extra for the call over and above the $29 fee he paid for 6 hours of wifi service.
The flight used Boeing's Connexion service. Skype sound quality was as good as ever - he didn't have a separate mic and was just using the built-in on his Mac Powerbook.
The PR from Lufthansa has this about the service:
The network from Cisco includes five Cisco Aironet 350 Access Points, a Cisco 3640 Router, and nine digital switches for the hardwired Ethernet connections found in some seats in First Class and Business Class. The wireless, obviously, reaches everyone on the plane. The data throughput for users on the plane is about 3 Megabits per second (Mbps) downstream and 128Kbps for uploads.
Clearly that's not enough for a plane-full of freephone callers, but if you're lucky enough to be one of the early adopters, it sounds great. Just hope that there are no international spammers or p2p nodes on board.
UPDATE 2/21: More notes:
We were both on the Mac OS X version of Skype, which does not yet have multiparty text IM - that would have been an ideal medium for the airplane narrowband environment when you are possibly juggling multiple calls in minimum time. As far as I'm concerned it's more about presence and real time communications in the air and less about whether you happen to have enough bandwidth to create a voice channel.
Some sites that picked up this article: Broadband Reports, asking "Will Connexion block VOIP traffic?"; Lifehacker saying "Fantastic use of Skype"; and the VOIP weblog asking whether people should be allowed to talk to people not right next to them on the flight. Om Malik writes: Time to kiss Verizon's Airfone goodbye.